3 Answers
3

If you have Google Talk or the Google Notifier installed, both of these have settings that allow GMail to be used as the default mail program.

For Internet Explorer, you'll need to use one of the options above.

For Firefox, you can use GMailTo or change the default client Firefox uses in the settings.

For Chrome, you have to use an extension that supports it. Better Gmail has a bunch of other features for GMail that let you do this. There is an official Send From GMail extension, and if you don't like that that adds a button to the toolbar, there is Send Using GMail which doesn't add that button.